Takabatake et al U.S. Pat. Nos. 3,927,223, Dowell 3,976,809, and Nakahira 3,977,660 are all directed to plasma spraying substrates, which are preferably metallic with a ceramic primer coat. Thereafter, a ceramic finish coat is applied by plasma spraying.
Hanson et al U.S. Pat. Nos. 3,192,892 and Ligenza 3,287,243 describe concepts for coating substrates, which are preferably metallic, with ceramic materials deposited by sputtering. However, neither of these patents is concerned with depositing on the sputter coated ceramic material a second ceramic coat which is sprayed by a plasma jet.